Under 64-bit Windows a 32-bit installer will use 32-bit registry only. If installer is 32/64 architecture aware, it'll install 64-bit application and use 64-bit registry. The 32-bit applications cannot see 64-bit registry and vice versa.

>Now if you install something, where does it register and how can you know? If an ActiveX somehow manages to get registered under 64-bit registry, it's invisible to 32-bit apps?